Preheat the oven to 200°C/gas mark 6. Toss the onion with the vinegar in a small bowl and set aside.
In a large bowl, combine the cauliflower, chickpeas and garlic with the baharat and oil. Spread out on a large baking tray and bake for 30 minutes or until the cauliflower is tender and starting to char, tossing halfway through. Leave to cool slightly.
In a small bowl, squeeze the roasted garlic out of their skins and mash together with the tahini. Add the lemon juice and gradually whisk in 40ml warm water, a little at a time, until the mixture is smooth and runny, but not too watery. Season.
Drain the onions and toss with the roasted cauliflower and chickpeas, spinach, parsley and raisins. Drizzle with the dressing and serve.